European Patent Application No. 124314A discloses such compounds possessing potent cardiotonic and antihypertensive activities as 2,4,4a,5-tetrahydro-7-(1H-imidazol-1-yl)-3H-indeno[1,2-c]pyridazin-3-one, and Journal of Medicinal Chemistry (J. Med. Chem.), vol. 24, P. 830 (1981) discloses immunosuppressive 2-(4-chlorophenyl)benzothiopyrano[4,3-c]pyrazol-3-one and so on.